The online continuous thickness measurement for a lamellar article such as a piece of paper, a note, a plastic to-be-tested film and a textile article becomes increasingly important in product production, detection, treatment and recycling, etc. At present, technologies for detecting a thickness of a to-be-tested film mainly include those using a Hall component, reflective ultrasonic detection, transmission ultrasonic detection, electromagnetic induction detection, eddy current detection and so on. However, the volume of detection devices corresponding to these technologies is large and the cost of detection devices corresponding to these technologies is high and thus are not beneficial to their applications hereto.
In recent years, a technology for detecting the thickness of the to-be-tested film via electrostatic induction between electrodes is under research and exploration continuously. For example, a Chinese Patent with the publication No. CN210302446Y discloses a capacitive paper thickness sensor, which is mainly to convert the change of a capacity of a capacitor into a change of an oscillation frequency and then convert the change of the frequency into a change of a voltage via a frequency-voltage conversion module. A Chinese Patent with the publication No. CN103363887A also discloses a material thickness detection method, which takes an electrode plate of a plate capacitor as a sensitive device for thickness detection and in which a displacement of a capacitive movable electrode plate caused by a thickness change of a measured object results in a capacity change of the plate capacitor.
With the above technology for detecting the thickness of the to-be-tested film via the electrostatic induction between the electrodes, the size of the detection device is reduced to a certain extent. However, the displacement of the capacitive plate still needs to be generated under the guidance of a mechanical device, which does not comply with the miniaturization development of the detection device. Moreover, the accuracy of the mechanical device determines the measurement accuracy to a large extent, particularly under conditions in which an article is under a high-speed transmission state, needs multipoint multi-channel accurate measurement and a measured object is extremely thin. The measurement accuracy of the above thickness sensor is relatively low. Besides, the mechanical device will generate a huge noise during high-speed working, which is not meet the development requirements of a modern industry on environmental protection and low carbon.